1. Field of the Invention
The present invention relates to an image pickup apparatus, an image pickup method, a program for implementing the method, and a storage medium storing the program. In particular, the present invention relates to an image pickup apparatus with an automatic focusing function, an image pickup method, a program for implementing the method, and a storage medium storing the program.
2. Description of the Related Art
In recent years, digital cameras as image pickup apparatuses have rapidly come into wide use; many of them have an automatic focusing function (hereinafter referred to as “the AF function”) irrespective of shape, technical specifications, and so forth. When a shutter button is pressed halfway, the digital camera uses a scanning method to calculate AF evaluation values over the entire driving range of a focus lens based on high-frequency components extracted from an image pickup signal from an image pickup device such as a CCD, drives the focus lens to a position where the highest AF evaluation value is obtained and fixes the focus lens there. Then, when the shutter button is deeply pressed, the digital camera can perform shooting (i.e. an image pickup operation which is intended to record an image of a subject in a recording medium) with the AF evaluation value being high. As a result, a photographer who shoots using the digital camera can easily take a picture in focus without skillful camera work.
Although the above-mentioned digital cameras have the AF function, a recorded image can be out of focus (hereinafter merely referred to as “blur”) due to motion of the entire camera caused by hand shake (hereinafter merely referred to as “shake”). Therefore, there has been proposed an image pickup apparatus which alerts a photographer to the shake when it is determined that a shot image is blurred due to failure in shooting (see Japanese Laid-Open Patent Publication (Kokai) No. H11-327024, for example).
Further, among the above-mentioned digital cameras, there is one which has a camera shake vibration absorbing function so as to suppress the effects of shake. This digital camera is provided with a detecting system which detects a shake, and a correcting system which makes a predetermined correction so as to compensate for the detected shake. There are the following two kinds of the detecting system: one which detects a shake using a velocity sensor such as a gyro sensor, and one which detects a shake through image processing according to a motion vector of an image. Also, there are the following two kinds of the correcting system: one which optically corrects light incident on a CCD, a film, or the like by moving a focus lens unit, and one which electrically corrects shot image data through image processing. A variety of correction modes have been devised using combinations of such detecting systems and correcting systems (see Japanese Laid-Open Patent Publication (Kokai) No. H06-98246).
The conventional digital cameras, however, use an external sensor, e.g. a velocity sensor such as a gyro sensor so as to detect a shake, and hence they cannot be small-sized.
Even if they can be small-sized, it is impossible to reliably detect a shake.